The proposed project is an extension of our studies of the regulation of transcription during development of the brine shrimp, Artemia salina. In this system, major quantitative changes in RNA synthesis in vivo are paralleled by changes in amounts of RNA polymerase activity measured in vitro, and by rates of RNA synthesis in isolated nuclei. Major objectives are the following: (1) define the mechanisms involved in regulating levels of RNA polymerase activity and numbers of enzyme molecules; (2) determine whether histones or other proteins are synthesized in large quantity at specific times during development. Synthesis and turnover of RNA polymerases will be studied by measuring incorporation of radioactive precursors into polypeptides identified as polymerase subunits. Antibody directed against Artemia RNA polymerases will be used to search for possible inactive precursor forms of polymerases in dormant encysted gastrulae. Radiolabeled protein fractions generated in studies of RNA polymerase synthesis will be surveyed for state-specific synthesis of other proteins. In particular, the expected temporal correlation of histone synthesis with DNA replication in early larvae will be examined.